JavaScript Source can be found in calculator.js
Check out version 1 to compare and contrast.
The usual rounding errors caused by the fact that the math is done by the computer in binary, and it converts to decimal. As long as you avoid irrational numbers like the square root of two (try squaring it) it seems to work great.
Parenthesis are a little goofy. You can't put another operator after the closing parenthesie, so any complex equation with parenthesis has to either multiply or the parenthesis have to be first.
If you enter a number and an operator, hit backspace, and try to enter a new operator, the new operator will replace the number you typed in. Quite an unfortunate bug; I will see about fixing it as soon as possible.
Handles more complex expressions like 5 - 4 * (20 - 19.5), including order of operations and parentheses.
update: these probably won't appear, since I'm no longer bored in visual basic class (not in vb class at all, yaay) and don't need distraction
Your standard "Remember this number for later, calculator!" type functions.
A complete TI-89 Emulator! (Probably involving a little server-side magic for graphing, so it won't all be in Javascript)
A completely customizable calculator, allowing you to basically rewire the entire thing!
Helpful-- something to the tune of, "You could have done 2x4" after you do 2+2+2+2. Note that it is only after you need the tip that it is offered :)